For situations in automotive technology and other fields in which safe and reliable functioning of control systems is of particular importance, such as for electronic control systems for airbags or other passenger restraint devices, control systems for automatic antilock braking systems (ABS), devices for vehicle dynamics control (ESP), or engine and transmission control systems, the so-called press-in technique, a cold contact method in which one or more projecting press-in pins for the electronic components are inserted with a press fit into complementary receiving openings in the printed circuit board, is being increasingly used for manufacturing high-quality electrical contacts between a printed circuit board and one or more electronic components subsequently installed on the printed circuit board. However, the press-in technique is also used in other fields for subsequent installation of electronic components on printed circuit boards, for example in controllers for power window modules or rear window washer systems in motor vehicles.
The press-in pins which are used have a press-in zone designed as a spring, which in the course of pressing the press-in pins into the receiving openings in the printed circuit board are pushed together transversally to the press-in direction, while the receiving openings, which are generally standard printed circuit board holes having a specific diameter, are expanded, a desired retaining force on the press-in pins in the receiving openings being ensured by the elastic and plastic deformation of the two joining partners.
Using this technique, an additional soldering process, so-called selective soldering, which severely stresses the printed circuit board, may be avoided in many cases. Furthermore, the electrical connections established using the press-in technique are characterized by defect-free contacting and very high reliability, and due to the gas-tight and therefore corrosion-resistant connection between the press-in pins and the printed circuit board have a reliably low transmission resistance over their projected service life. In addition, press-in connections are elastic, thus allowing the interruptions and contact failures which frequently occur in soldered connections as the result of mechanical and thermal stresses during operation to be avoided.
However, due to the high press-in forces of approximately 70 to 180 N/pin which are necessary for pressing in conventional press-in pins, the regions of the printed circuit board bordering the receiving openings are also subjected to high shear forces in the direction of the press-in forces. On the one hand, these forces compel circuit designers to provide larger “off-limit zones” on the surfaces of the printed circuit board, around the junctions of the receiving openings, to avoid the occurrence of cracks in soldered-on components as the result of surface tensile stresses in the printed circuit board or a surface-printed circuit or printed conductor. As a result, however, it is possible that a portion of the printed circuit board surface is not able to be used as a circuit surface. On the other hand, due to high localized mechanical stress on the printed circuit board around the receiving opening, pushing in a press-in pin results in a so-called “jet effect,” a deformation of the printed circuit board bordering the receiving opening caused by shear forces. For multilayer printed circuit boards, this jet effect entails the risk of conductive metallic inner layers breaking away as the result of extreme tensile stresses. In addition, there is the risk that a soft metallic sliding layer on the surface of the press-in pins, necessary for pressing in the pin in an operationally reliable manner, may be partially scraped away from the pins when being pressed in from the opening edges of the receiving openings, thus forming chips or flakes which under unfavorable conditions may result in short circuits at other locations on the printed circuit board, and thus, functional failure.
On this basis, an object of the present invention is to improve a press-in pin and a method of the type described at the outset in such a way that the above-referenced disadvantages may be avoided.